For studying the role of cachectin/Tumor Necrosis Factor -TNF in septic shock we have developed a physiological monitoring system for laboratory rats. Temperature and direct arterial pressure were monitored. Special carotid/aortic catheters were designed and tested for frequency response. New catheters are supplied on a continuous basis. During actual studies, septic shock was induced and physiologically characterized. Current studies center around repetitive administration of recombinant TNF and the effects of rTNF on mortality and morbidity of gram negative sepsis.